A solution of sulfuric acid and the like are often heated to use at a high temperature as a cleaning liquid in the resist stripping process in the semiconductor manufacturing. Particularly, in a process of heating a sulfuric acid solution containing persulfuric acid (peroxodisulfuric acid and peroxomonosulfuric acid are collectively referred to as persulfuric acid.) obtained by electrolyzing a sulfuric acid solution to obtain high oxidizing property, it is desired to rapidly heat the sulfuric acid solution containing persulfuric acid in a few seconds to supply the solution to the resist stripping process. Patent Document 1 proposes a liquid heating device capable of heating the sulfuric acid solution containing persulfuric acid in a short period to a high temperature.
When the sulfuric acid solution containing persulfuric acid is heated, a residence time of the sulfuric acid solution containing persulfuric acid in the heating device is preferably reduced by reducing a thickness of a heating liquid flow passage to rapidly heat the sulfuric acid solution containing persulfuric acid. Moreover, the persulfuric acid is preferably prevented from decomposing by itself due to a high temperature near a heat conduction surface by heating not with heat transfer by conduction by means of a heat transfer plate and convection, but with radiant heat.